Antenna



Dec. 25, 1928. 1,696,234

R. A. HEISING ANTENNA Filed on. 18, 1923 lnven' for I lwmondA/fe/smgby-fim 40) Patented Dec. 25, 1928.

UNITED STATES PATENT OFFICE.

RAYMOND A. HEISING, OF MILLBURN, NEW JERSEY, ASSIGNOR TO WESTERN ELEC-TRIC COMPANY, INCORPORATED, OF NEW YORK, N, Y., A CORPORATION 015 NEWYORK.

ANTENNA.

Application filed October 18, 1923. .Serial No. 669,220.

This invention relates to radio transmission by means of verticalantennae or antennae having both a vertical and a horizontal portion.

The invention more particularly relates to means for avoidingdifficulties in operating at wave lengths near to or shorter than thefree period of the upper part of an antenna.

In such radio systems, where an openantenna is used at a higherfrequency than the natural frequency, the upper part of the antenna mayact as a loop resonant circuit, tending toincrease the effectiveresistance 1 and to lower the effective height of the antenna. Aconsequence of this action is that the loop resonant circuit makes theapparent resistance of the antenna abnormally high. Proper radiationthen does not occur.

The explanation of this phenomenon is understood to be as follows, butin stating the probable theory it is not the intention to limit theinvention, but rather to state the theory as the probable explanationofthe operation of the apparatus.

It is believed that certain parts or sections of antennae have capacitybetween them and that the inductance of theseparts or sections and ofthe conductor connecting them is of such a value as to cooperate withthe capacity to form a tuned circuit which. acts as a tuned loop inseries in the antenna. Such an inherent tuned circuit may be termedaparasitic tuned circuit, thereby suggesting that itis undesired anddetrimental to the best operation of the system. lVhether thls thcory iscorrect or not it appears that at frequencies at and above the naturalfrequency of an antenna some effect of this kind is present which,renders the antenna inefficient as a radiating element and which rendersit difficult to transfer energy into the antenna. 1

An object 'of the invention is, therefore, to decrease the effectiveresistance and to increase the effective height and consequently toincrease the radiating efliciency of an antenna at high fre uencies.

To accomplish t 118 result, it is proposed to load the antenna with aplurality of capacities arranged in series and spaced at shortintervals, along the vertical portion of the antenna and if necessaryalong the horizontal portion also.

form of radio transmission system having the elements constituting theinvention embodied therein.

Flg. 1 1s a circuit diagram illustrating the invention as applied to anantenna with a.

flat topped portion; Fig. 2 is a modified form thereof, as applied to avertical anten-' na, the supporting elements for the antenna beingomitted; Figs. 3 and 4 are diagrams referred to hereinafter inexplaining the theoretical aspects of the invention; and Fig. 5 is acircuit diagram of the invention as applied to an antenna having afiattopped portion consisting of a plurality of conductors.

Referring toFig. 1 the circuit 1 represents a low frequency circuit orsource, of signal waves comprising microphone 2, source of. directcurrent 8, andprimary of transformer 4. The high frequency circuit 5includes a source of high frequency carrier waves 6 and primary oftransformer 7 By means of transformers l and 7 the low frequency orsignaling waves and the high frequency or carrier waves are impressedupon the modulating and amplifying device 8. This device may be anymodulation system such as of the well known type, disclosed in thepatent to Schelleng, No. 1,437,021, granted November 28, 1922. Theentire transmission apparatus 14 typifies any source of waves to beradiated. The modulated waves are impressed, by means of the transformer9, up-

on the antenna. circuit which comprises a lll an antenna loaded withcapacities C, arranged in series and spaced apart at intervals. Themodulated waves from the source 14 are impressed upon the antenna bymeans of the transformer 9.

Fig. 3 is a diagramillustrating the reason why the effective resistanceof an antenna of the type of Fig. 1 increases at short wave lengths. Theprincipal aerial-to-grouml ca pacity of the antenna is represented bycapacity 15. The parts of the antenna have capacity between them asindicated by the dotted capacities 1S and the inductance of theconductor cooperates with the capacities to form a loop-resonant circuitof one or more degrees of freedom. The parts 14- and 9 correspond to thesimilarly numbered portion of Fig. 1. The tuned circuit thus formed maybe two-branched, having one branch including the left hand capacity 18,the inductance of the left hand horizontal portion, and the inductanceof the upper vertical portion. The other branch includes the right handcapacity and the inductance of the right hand horizontal portion and theupper vertical portion. Inasmuch as the vertical lead is usuallyconnected to the horizontal part of an antenna near one end thereof, oneof these branches will usually be absent. However this discussion ofFig. 3 indicates that the principles of the invention apply to caseswhere the parasitic tuned circuit has several degrees of freedom.

Fig. 4 is a circuit diagram for elucidating the action of a verticalantenna such as that of Fig. 2 when the capacities constituting thepresent invention are not applied thereto. The capacity 17 representsthe capacity between the upper part of the vertical lead 10 and a partlower down on the vertical lead 10 but above the coupling transformer 9.The inductance 16 represents the distributed inductance of the verticalportion. The inductance 16 and capacity 17 combine to form a resonantcircuit. At and around the free period of this circuit it becomes verydifficult to secure proper radiation because the reactance of theantenna changes at certain frequencies to inductive reactance, theresistance increases, and the effective height decreases. The capacity15 constitutes the principal antenna-ground capacity of the antenna.

hen condensers are included in circuit as in Figs. 1 and .2, theresonant effects described in connection with Figs. 3 and 4 will beabsent or will occur only at much higher frequencies so that the upperlimit of the working frequency range is much extended.

Fig. 5 shows a complete antenna comprising a vertical portion or lead 10and horizontal conductors 11 loaded with a plurality of capacities C,arranged in series and spaced at intervals along both the vertical andhorizontal portions. The vertical lead is joined to the horizontalportion in the conventional manner. shown here as being connectedthereto at an intermediate point of the horizontal portion. Theoperation of the arrangement of Fig. 5 will he understood from aconsideration of the discussion of Figs. 1 and 3.

The condensers C may consist of strain condensers of sutlicientme-hanical strength to withstand the pull of the antenna con ductors oralternatively they may consist of relatively weal: mechanicalstructures. In the latter case the sections of the antenna between whichcondensers are to be placed will be separated by suitable insulatorsaround which the condensers are shunted.

Having described the invention in detail, the various features andcombinations inherent therein which are believed to be novel andpatentable are set forth in the 'appended claims.

What is claimed is:

1. In an open radiating circuit for transmitting at short wave lengths,means for increasing the effective natural frequency of said circuitcomprising a plurality of capacities included in series in said circuitand spaced apart from each other, the inductance and capacity of theportions of said circuit between said spaced capacities being too smallto form an element which can be self-resonating at any wave length inthe neighborhood of the short wave lengths employed.

2. ,In an open transmitting antenna, means forincreasing the upper limitof the frequency range over which the antenna can be worked comprising aplurality of small capacities arranged in series in the open antenna atspaced intervals, said capacities being of such value that thercactzrnce of each of the sections of said antenna measured in serieswith an adjacent capacity is capacitative at the desired workingfrequency.

In witness whereof, I hereunto subscribe my name this 17th day ofOctober, A. 3)., 1923.

RAYMOND A. HEISING.

